JPS5896618A - Manufacture of cement dispersant - Google Patents

Abstract

PURPOSE:To obtain a cement dispersant consisting mainly of a cndensate, by the condensation, under inert gas-pressurized state between naphthalenesulfonic acid and formaldehyde to reduce reaction time and markedly decrease the amount of the catalyst, i.e. sulfuric acid to effect easier after-treatment. CONSTITUTION:To naphthalenesulfonic acid, ca. 0.01-0.5 (pref. 0.04-0.4)mol, per mol of the above acid, of sulfuric acid as a catalyst is added and then water of ca. 0.15-0.5 time for the weight of the naphthalene sulfonic acid is added followed by incorporating ea. 0.8-1.2 (pref. 0.9-1.1)mol, in terms of formaldehyde, of ca. 37% formalin to carry out a reaction under a pressure >=0.2 (pref. 0.5- 10)kg/cm<2>G of an inert gas (e.g., nitrogen) at[a. 100-140 (pref. 110-130) deg.C for 2-16 (pref. 3-10)hr, thus obtaining a condensate and its salt C the objective cement dispersant). USE:For the application to concrete, mortor, cement paste, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a cement dispersant containing a naphthalene sulfonic acid-formaldehyde condensate and its salts as a main component.

Adding a cement dispersant during mixing of concrete increases the softness of the concrete, improving workability, reducing the amount of water required for concrete, increasing the strength of concrete, increasing watertightness, This results in a variety of favorable results, including reduced cracking. For this reason, cement dispersants are widely and commonly used today.

It has been known that the condensate obtained by condensing naphthalene sulfonic acid and formaldehyde (hereinafter referred to as NFC) and its salts have performance as a cement dispersant. It was also known that NFC exhibited excellent performance especially as a cement dispersant.
-9564).

Generally, NFC is obtained by a condensation reaction between naphthalene sulfonic acid and formaldehyde at 95 to 100°C in the presence of sulfuric acid. It was necessary to use a large amount of sulfuric acid and conduct the condensation reaction for a long time. For example, the above-mentioned Special Publication No. 41-11737, Special Publication No. 1
According to Example @48-9564, 1 mol of naphthalene sulfonic acid and 79 mol of naphthalene sulfonic acid were present during the condensation reaction, and the reaction time was 25 hours or more. Therefore, the post-treatment of large amounts of sulfuric acid became a problem as well as the need for a long reaction time. That is, since a large amount of sulfuric acid is used, when the reaction product after the condensation reaction is subjected to lye-sodification, a large amount of gypsum is produced as a by-product, which is difficult to filter and dispose of. Another method for post-processing the reaction product is to neutralize it by adding sodium hydroxide, but a large amount of sodium sulfate is produced as a by-product, and sodium sulfate precipitates in cold weather, which interferes with the handling of the NFC salt solution. caused.

As a result of various studies to solve these problems, the present inventors shortened the condensation reaction time by sealing an inert gas during condensation and performing a pressurized reaction at a condensation reaction temperature of 100 to 140'C. It was discovered that the amount of sulfuric acid could be greatly reduced and the present invention was completed.

The present invention is a method for producing a cement dispersant containing a naphthalene sulfonic acid-formaldehyde condensate and its salts as main components, which is characterized by condensing naphthalene sulfonic acid and formaldehyde under pressure of an inert gas.

In the present invention, the naphthalene sulfonic acid is preferably a pure product, but it is preferable to use a sulfonated product of hexathalene containing alkylnaphthalene, etc., as long as it does not impair the effects of the present invention or cement dispersibility. In the condensation reaction of sulfonic acid and formaldehyde, it is preferable to use sulfuric acid as a catalyst due to advantages such as shortening of reaction time.

In the present invention, the inert gas includes nitrogen, carbon dioxide,
A gas such as helium or argon is used. The inert gas in the present invention is not limited to those mentioned above, but refers to any gas that does not have a bad influence on the condensation reaction. The pressure of the inert gas is 0.2 kg/cjG or higher, preferably α5 to 10 cm-G.

NFC is manufactured by the method of the present invention as follows. 1 mol of naphthalene sulfonic acid and 0.01-0.5 mol using sulfuric acid as a catalyst, preferably 0.04-0.4 mol
0.15 to 0.5 times the weight of naphthalene sulfonic acid is added to give about 371 formalin as formaldehyde, preferably 0.
．． Adding 9 to 1.1 mol of inert gas and enclosing 0.2 to 10 or more, preferably 0.5 to 10 kfaiG of inert gas makes it difficult to obtain a preferable NFC from both physical properties and performance;
If it exceeds cd G, it is impractical from the economic and safety aspects of the equipment. The reaction temperature is preferably 100 to 140°C, preferably 110 to 130°C. If the temperature is less than 100°C, the reaction rate will be slow and the effect of the present invention will not be exhibited.
If the temperature exceeds 0°C, the reaction rate becomes too fast, it is difficult to control the reaction, and NFC becomes highly viscous, which is not practical. The reaction time varies depending on factors such as catalyst amount and temperature, but from 2 to 16
Preferably, the appropriate time is 3 to 10 hours. If the viscosity of the reactants increases during the condensation reaction, making stirring difficult, add a small amount of water to make stirring easier. Also, water can be added in advance to carry out the reaction smoothly and easily. After the reaction is complete, add a predetermined amount of water to the desired concentration to dilute, neutralize with alkali, and then crystallize and remove the sodium sulfate at 0°C, or add liming soda according to the usual method. I went and got a 4. NFC obtained by the method of the present invention is used in the form of Na salt as well as K%NH
4. Can also be used in the form of C4 salt.

The production method of the present invention can greatly shorten the condensation time,
Moreover, NFC exhibiting excellent performance as a cement dispersant in the presence of a small amount of sulfuric acid can be obtained, and the manufacturing cost of NFC can be extremely reduced compared to conventionally known methods.

In addition to being used for concrete, the dispersant of the present invention has the same effect as for concrete even when added to mortar, cement paste, etc.

The effects and advantages of the present invention compared with conventionally known methods are listed below.

0) In the conventional method of condensation reaction, the temperature is
If the temperature exceeds ℃, formaldehyde or methanol, which is a stabilizer for formalin, will foam, and in severe cases,
There was a phenomenon that the contents were blown out, and the condensation reaction could not be carried out at a temperature of 100°C or higher. On the other hand, if the reaction is carried out while suppressing the above-mentioned foaming phenomenon by pressurizing with an inert gas as in the present invention, the condensation temperature can be raised.

In addition, by raising the condensation temperature, the viscosity of the reactant can be reduced, so that the stirring condition is good and the reaction proceeds uniformly.

(b) In the conventional method, the liquid level of the reactants rises as the condensation reaction progresses and the viscosity increases, but in the pressurized reaction of the present invention,
is almost constant.

e9 In the conventional method, the temperature was raised to 100℃ using only self-pressure in a closed system.
When the above condensation reaction is carried out, foaming occurs, the stirring condition worsens, local heating occurs, and a part of the reactant tends to turn into resin, but the method of the present invention, in which inert gas is enclosed, prevents these phenomena. It can be prevented.

b) In the reaction of conventional methods, when the viscosity of the reactant increases, local heating phenomenon occurs, and a part of the reactant tends to turn into resin, but the pressurized reaction of the present invention can prevent the local heating phenomenon. .

(f) In the pressurized reaction of the present invention, the condensation reaction temperature can be raised, so the amount of sulfuric acid as a catalyst can be greatly reduced, and its concentration is less than 50% before and after the addition of hol-v IJ. , and the reaction time can be shortened.

(F) Since less sulfuric acid is used, the amount of by-product sulfate is reduced, making post-treatment easier. For example, the amount of sulfuric acid present as a catalyst per mole of naphthalenesulfonic acid is 0.
．． When neutralized with IJium, there is less sodium sulfate as a by-product, so it does not precipitate even when cooled to 0°C, and post-treatment is unnecessary or simple. becomes.

Next, the present invention will be explained by giving examples and comparative examples. However, the present invention is not limited to this in any way.

Example 1 (1) Production of NPC 200 tons of naphthalene was heated to 115-120°C to melt it, and 200 f of 98-sulfuric acid was added at a temperature of 120-130°C.
was added over a period of 1 hour, the temperature was raised to 160°C over 1 hour, and the reaction was continued at the same temperature for 6 hours. After cooling to 120-130°C, 199 g of 9891 monosulfuric acid was added, and then 781 g of water was added.

The temperature was cooled to 80 to 90°C, kept warm, and 37% formalin 127f was added dropwise over 3 hours.

After dropping, 120 f of water was added, and then nitrogen was introduced.3.
It was set to 0 kg/cjG. Next, the temperature was raised to 115°C, and a feeding reaction was carried out at this temperature for 4 hours.

After condensation, neutralize with sodium hydroxide solution,
Sodium sulfate was crystallized and removed at 0°C.

Roro Concrete Test (1) Concrete materials/cement: Onoda, Asano, and Sumitomo ordinary Portland cement were mixed in equal amounts.

Fine aggregate: Ubukawa sand coarse aggregate for Oi; Crushed stone from Ome (maximum size 20 m) (2) Concrete mixing conditions Unit cement amount: 450 Kangiku 3 Unit water f: 156 kg/ms Fine aggregate ratio: 42 % NFC Addition amount: 1 part by weight of 0.5 weight (calculated as solid content) per 100 parts by weight.

(3) Test method Based on the materials used and the blending conditions described above, 50 was mixed continuously for 90 seconds after adding all the ingredients using a strongly controlled mixer. The slump test was conducted in accordance with JISA-11011' - Concrete slump test method, and the amount of air was determined using a rod vibrator for compaction.
Measurements were made in accordance with ``Test method using pressure of air volume of unhardened concrete''. Furthermore, the compressive strength is JIS
A-1132r Concrete Strength Test Specimen Preparation A Φ10 x 20m specimen was prepared according to J
ISA-1108r concrete compressive strength test method”
Compressive strength was measured at 3 days, 7 days and 28 days of age. In addition, when preparing the specimen, a rod-shaped vibrator was used.
Compaction was performed using

Example 2 200 tons of naphthalene is heated to 115-120°C and melted, and 122f of 25% oleum is added at a temperature of 120-130°C.
was added over a period of 1 hour, the temperature was raised to 160° C. over 1 hour, and the reaction was continued at the same temperature for 4 hours. After cooling to 100-110°C, 4Of of water was added, the temperature was cooled to 80-90°C, kept warm, and 127f of 37-thiformalin was added dropwise over 3 hours. After the dropwise addition, nitrogen was introduced to bring the temperature to 30°C to 4idG, and then the temperature was raised to 115°C, and a feeding reaction was carried out at this temperature for 5 hours.

After condensation, neutralize with sodium hydroxide solution and reduce to 0.
Although it was cooled to ℃, there were no crystallized substances.

Examples 3 to 5 and Comparative Example 1 Reactions were conducted in the same manner as in Example 1 while changing the molar ratio of raw materials, reaction conditions, etc. as shown in Table 1. The results are also listed in Table 1. As seen in the same table, it can be seen that the method of the present invention achieves the same or better performance of cement dispersant in a shorter reaction time than that of the comparative example.

Claims (1)

[Claims] A method for producing a cement dispersant containing a naphthalene sulfonic acid-formaldehyde condensate and its salts as a main component, which comprises condensing naphthalene sulfonic acid/acid and formaldehyde under pressure of an inert gas.